With the growth of the information industry, demands for increasing the storage or memory capacity in an information storage device have come to know no limits. For example, while storing a picture image requires an enormous amount of memory capacity, the future information industry is calling for storing highly detailed images, images enormous in number and dynamic picture images over an extended time period, much more than those at the present time.
Large-capacity information storage devices includes a magnetic memory or storage in which information is written and reproduced by utilizing the magnetooptic effect (Faraday effect or magnetooptic Kerr effect) and which being large in storage capacity is predicted to continue to be the leading information storage in the future as well. In order to meet with the demands in the future for increasing the memory capacity in such a magnetic storage, it is vital to make smaller the storage unit of information, namely the size of a memory device. And it is expected, for example, that an element of the memory device will have to be 30 nm (300 angstroms) in magnetic medium size to meet a requirement for 100 G bits/square inches in the year 2001 and 10 nm (100 angstroms) in magnetic medium size to meet a requirement for 1000 G bits/square inches in the year 2007.
It has so far been known that a magnetic material which exhibits the magnetooptic effect makes it possible to write and reproduce information, by using in a form of, for e.g., a magnetooptic disk. Increasing of the information storage capacity of a memory device requires making its element size smaller which, however, makes a readout signal smaller. Consequently, a magnetic material is made necessary that is larger in the magnetooptic effect exhibited in inverse proportion to the device size. As a measure taken to this end it has been proposed as shown in JP H05-135569 A to make a memory device utilizing the anomalous Hall effect that is an effect based on the spin-orbit interaction in a solid. While such magnetooptic effect have been found to exhibit the effect to a greater extent than the earlier devices, it is still necessary to have their element size as large as 100 angstroms, so, their exhibiting magnetooptic effect is far less sufficient in intensity to realize a memory with a storage capacity of several terabits per square inches or more needed in the future, which problems remain unsolved.